Sheath system for catheter pump

ABSTRACT

A catheter pump assembly is provided. The catheter pump assembly includes a proximal portion, a distal portion, a catheter body having a lumen extending along a longitudinal axis between the proximal and distal portions, an impeller disposed at the distal portion, and a stator disposed at a downstream location of the impeller to straighten flow downstream from the impeller. The stator is collapsible from a deployed configuration to a collapsed configuration.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/330,057, filed on May 25, 2021, which is a continuation of U.S.patent application Ser. No. 15/840,117, filed on Dec. 13, 2017, which isa continuation of U.S. patent application Ser. No. 13/801,833, filed onMar. 13, 2013, which claims the benefit of U.S. Provisional PatentApplication No. 61/646,789, filed on May 14, 2012, all of which areincorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

This application is directed to a catheter pump for mechanicalcirculatory support of a heart, and related components, systems andmethods. In particular, this application is directed to reliablecoupling of components that are subject to dynamic loads applied betweena plurality of catheter bodies.

Description of the Related Art

Heart disease is a major health problem that has high mortality rate.Physicians increasingly use mechanical circulatory support systems fortreating heart failure. The treatment of acute heart failure requires adevice that can provide support to the patient quickly. Physiciansdesire treatment options that can be deployed quickly andminimally-invasively.

Intra-aortic balloon pumps (IABP) are currently the most common type ofcirculatory support devices for treating acute heart failure. IABPs arecommonly used to treat heart failure, such as to stabilize a patientafter cardiogenic shock, during treatment of acute myocardial infarction(MI) or decompensated heart failure, or to support a patient during highrisk percutaneous coronary intervention (PCI). Circulatory supportsystems may be used alone or with pharmacological treatment.

In a conventional approach, an IABP is positioned in the aorta andactuated in a counterpulsation fashion to provide partial support to thecirculatory system. More recently minimally-invasive rotary blood pumphave been developed in an attempt to increase the level of potentialsupport (i.e. higher flow). Rotary pumps have become more commonrecently for treating heart failure. A rotary blood pump is typicallyinserted into the body and connected to the cardiovascular system, forexample, to the left ventricle and the ascending aorta to assist thepumping function of the heart. Other known applications include pumpingvenous blood from the right ventricle to the pulmonary artery forsupport of the right side of the heart. An aim of acute circulatorysupport devices is to reduce the load on the heart muscle for a periodof time, to stabilize the patient prior to heart transplant or forcontinuing support. Rotary blood pumps generally utilize an electricmotor which drives an impeller pump at relatively high speeds. In thecase where the pump is remote from the motor, for example where theimpeller is in the body and the motor is outside the body, there is aneed for a robust and reliable connection between the motor and theimpeller. There may also be the need for forming a flexible connectionbetween the motor shaft and the impeller to allow free movement ofvarious pump components during use and when pushing through thevasculature to the treatment location. There is also the continuing needto provide these system components in a compact, efficient form factorto allow for percutaneous approaches.

There is a need for improved mechanical circulatory support devices fortreating acute heart failure. Fixed cross-section ventricular assistdevices designed to provide partial or near full heart flow rate areeither too large to be advanced percutaneously (e.g., through thefemoral artery without a cutdown) or provide insufficient flow.

SUMMARY OF THE INVENTION

An aspect of at least one of the embodiments disclosed herein is therealization that the connection of a flexible proximal body to a morerigid distal segment of a catheter assembly can be better secured with arobust mechanical interface between one or more features of thesecomponents. For example, a distal end of the flexible proximal body canbe fitted with a device or structure providing an interface thatmechanically engages the flexible proximal body and that can be directlyjoined, e.g. welded, to a structure to which a load is applied.

In one embodiment, a catheter pump assembly is provided that includes anelongate polymeric catheter body, a cannula, and a tubular interface.The elongate polymeric catheter body has a proximal end and a distalend. The cannula has an expandable portion disposed distally of theelongate polymeric catheter body. The cannula can also have anothertubular portion that is proximal to the distal portion. The tubularinterface has an outer surface configured to be joined to the tubularportion of the cannula and an inner surface. The inner surface isdisposed over the distal end of the elongate polymeric catheter body.The tubular interface has a plurality of transverse channels extendingoutward from the inner surface of the tubular interface. An outersurface of the elongate polymeric catheter body projects into thetransverse channels to mechanically integrate the elongate polymericcatheter body with the tubular interface.

In another embodiment, a catheter pump assembly is provided thatincludes an elongate polymeric catheter body, a tubular member, and amechanical interface. The elongate polymeric catheter body has aproximal end and a distal end. At least a portion of the tubular memberis disposed distally of the elongate polymeric catheter body. Themechanical interface is disposed between a portion of the elongatepolymeric catheter body and the tubular member. The mechanical interfaceis configured to mechanically integrate with a surface of the elongatepolymeric catheter body.

In another embodiment, a catheter pump assembly is provided thatincludes an elongate catheter body, a metallic tubular member, and firstand second mechanical interfaces. The elongate catheter body has aproximal portion and a distal portion. The metallic tubular member isdisposed at least partially distally of the elongate catheter body. Thefirst mechanical interface has a first portion joined to the distalportion of the elongate catheter body and a second portion welded to themetallic tubular member. The second mechanical interface is disposed onan outside surface of the catheter pump assembly. The second mechanicalinterface has a deflectable member configured to be disposed adjacent tothe outside surface of the catheter pump assembly in a firstconfiguration. The deflectable member is configured to be disposedinward of the outside surface of the catheter pump assembly in a secondconfiguration. When in the second configuration, the deflectable membermechanically and securely engages the outside surface of the catheterpump assembly with a structure disposed inward of the second mechanicalinterface.

In another embodiment, a method is provided for coupling components of acatheter pump assembly together. An elongate polymeric tubular body isprovided that has a proximal end and a distal end. A metallic tubularbody is provided that has a proximal portion and a distal portion. Amechanical interface having a first interface zone and a secondinterface zone is positioned such that the first interface zone isdisposed over a portion of the elongate polymeric tubular body adjacentto the distal end thereof. The polymer is then caused to flow into thefirst interface zone, whereby the elongate polymeric tubular bodybecomes joined with the first interface zone of the mechanicalinterface. The metallic tubular body is coupled with the secondinterface zone of the mechanical interface.

In one approach, the polymer is caused to flow by heating the elongatepolymeric tubular body to cause at least a portion of elongate polymerictubular body adjacent to the distal end thereof to transition to a statewith low resistance to deformation.

In another embodiment, a catheter pump assembly is provided thatincludes a proximal portion, a distal portion, and a catheter bodyhaving a lumen extending therebetween along a longitudinal axis. Thecatheter pump assembly also includes a torque assembly that has a firstportion disposed in the lumen of the catheter body and a second portiondisposed distal of the first portion. The second portion coupled with animpeller. The torque assembly causes the impeller to rotate uponrotation of the first portion of the torque assembly. The catheter pumpassembly also includes a thrust bearing and a thrust bearing brace. Thethrust bearing is disposed within the catheter pump assembly adjacent tothe distal end of the catheter body. The thrust bearing resists movementof the torque assembly along the longitudinal axis. The thrust bearingbrace is disposed on the outside surface of the torque assembly. Thethrust bearing brace has a distal face that is directly adjacent to aproximal face of the thrust bearing.

In another embodiment, a catheter assembly is provided that includes anelongate flexible body, a torque assembly, a bearing assembly, and asleeve. The elongate flexible body is disposed along a proximal portionof the catheter assembly and has a proximal infusate channel formedtherein. The torque assembly extends through the elongate flexible body.The bearing assembly comprises a housing having an outer surface and abearing surface disposed within the housing. The bearing surfaceprovides for rotation of the torque assembly within the bearing housing.The sleeve comprises and an inner surface configured to be disposed overthe outer surface of the housing of the bearing assembly and a fluidcommunication structure that extends through the walls of the sleeve.The catheter assembly also includes a distal infusate channel in fluidcommunication with the proximal infusate channel, the distal infusatechannel disposed over the outer surface of the bearing housing andthrough side walls of the slot.

In another embodiment, a catheter pump assembly is provided thatincludes a proximal portion, a distal portion, and a catheter bodyhaving a lumen extending along a longitudinal axis between the proximaland distal portions. The catheter pump assembly also includes animpeller disposed at the distal portion and a stator disposed distal ofthe impeller to straighten flow downstream from the impeller. The statoris collapsible from a deployed configuration to a collapsedconfiguration.

In another embodiment, a catheter system is provided that includes anelongate polymeric catheter body, a cannula, and at least one expandablecomponent disposed within the cannula. The elongate polymeric catheterbody has a proximal end and a distal end. The cannula has an expandableportion disposed distally of the elongate polymeric catheter body. Thecatheter system also includes an elongate sheath body that has aretracted position in which the elongate sheath body is proximal of theexpandable portion of the cannula and the at least one expandablecomponent and a forward position in which the elongate sheath body isdisposed over the expandable portion of the cannula and the at least oneexpandable component. A first segment of the elongate sheath bodydisposed over the expandable portion of the cannula and the at least oneexpandable component is configured to resist kinking to a greater extentthan a second segment of the elongate sheath body disposed adjacent tothe first segment.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the subject matter of this applicationand the various advantages thereof can be realized by reference to thefollowing detailed description, in which reference is made to theaccompanying drawings in which:

FIG. 1 illustrates one embodiment of a catheter pump configured forpercutaneous application and operation;

FIG. 2 is a plan view of one embodiment of a catheter adapted to be usedwith the catheter pump of FIG. 1 ;

FIG. 3 show a distal portion of the catheter system similar to that ofFIG. 2 in position within the anatomy;

FIG. 4 is a perspective view of a distal portion of a catheter assemblyaccording to one embodiment;

FIG. 5 is a perspective partial assembly detail view of a portion of thecatheter assembly of FIG. 4 .

FIG. 6 is a cross-sectional view of a portion of a connection zone ofthe catheter assembly of FIG. 4 .

FIG. 6A is a schematic view of embodiments of an outer sheath configuredto enhanced delivery and retrieval performance.

FIG. 7 is a perspective view of a distal portion of a catheter assemblyaccording to another embodiment;

FIG. 8 is a perspective partial assembly detail view of a portion of thecatheter assembly of FIG. 7 ;

FIG. 9 is a detail view of a mechanical interface of a catheterassembly;

FIG. 10 is a cross-sectional view of a portion of a connection zone ofthe catheter assembly of FIG. 9 ;

FIGS. 11-14 illustrate features of additional embodiments of catheterassemblies having robust mechanical interface; and

FIGS. 15-17 illustrate features of additional embodiments of catheterassemblies having robust mechanical interface.

More detailed descriptions of various embodiments of components forheart pumps useful to treat patients experiencing cardiac stress,including acute heart failure, are set forth below.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A high performance catheter pump is desired to provide sufficient outputto approach and in some cases exceed natural heart output. Performanceof this nature can be achieved with inventive components disclosedherein.

FIGS. 1-3 show aspects of a catheter pump 10 that can provide highperformance including flow rates similar to full cardiac output. Thepump 10 includes a motor driven by a controller 22. The controller 22directs the operation of the motor 14 and an infusion system 26 thatsupplies a flow of infusate in the pump 10. A catheter system 80 thatcan be coupled with the motor 14 houses an impeller within a distalportion thereof. In various embodiments, the impeller is rotatedremotely by the motor 14 when the pump 10 is operating. For example, themotor 14 can be is disposed outside the patient. In some embodiments,the motor 14 is separate from the controller 22, e.g., to be placedcloser to the patient. In other embodiments, the motor 14 is part of thecontroller 22. In still other embodiments, the motor is miniaturized tobe insertable into the patient. Such embodiments allow the drive shaftto be much shorter, e.g., shorter than the distance from the aorticvalve to the aortic arch (about 5 mm or less). Some examples ofminiaturized motors catheter pumps and related components and methodsare discussed in U.S. Pat. Nos. 5,964,694; 6,007,478; 6,178,922;6,176,848; and all of which are hereby incorporated by reference hereinin their entirety for all purposes.

FIG. 3 illustrates one use of the catheter pump 10. A distal portion ofthe pump 10 is placed in the left ventricle LV of the heart to pumpblood from the LV into the aorta. The pump 10 can be used in this way totreat patients with a wide range of conditions, including cardiogenicshock, myocardial infarction, and acutely decompensated heart failure,and also to support a patient during a procedure such as percutaneouscoronary intervention. One convenient manner of placement of the distalportion of the pump 10 in the heart is by percutaneous access anddelivery using the Seldinger technique or other methods familiar tocardiologists. These approaches enable the pump 10 to be used inemergency medicine, a catheter lab and in other non-surgical settings.

FIG. 2 shows features that facilitate small blood vessel percutaneousdelivery and high performance up to and in some cases exceeding normalcardiac output in all phases of the cardiac cycle. In particular, thecatheter system 80 includes a catheter body 84 and a sheath assembly 88.An impeller assembly 92 is coupled with the distal end of the catheterbody 84. The impeller assembly 92 is expandable and collapsible. In thecollapsed state, the distal end of the catheter system 80 can beadvanced to the heart. In the expanded state the impeller assembly 92 isable to pump blood at high flow rates. FIGS. 2 and 3 illustrate theexpanded state. The collapsed state can be provided by advancing adistal end 94 of an elongate body 96 distally over the impeller assembly92 to cause the impeller assembly 92 to collapse. This provides an outerprofile throughout the catheter assembly 80 that is of small diameter,for example 12.5 French as discussed further below.

In some embodiments, the impeller assembly 92 includes a self-expandingmaterial that facilitates expansion. The catheter body 84 on the otherhand preferably is a polymeric body that has high flexibility. When theimpeller assembly 92 is collapsed, as discussed above, high forces areapplied to the impeller assembly 92. These forces are concentrated at aconnection zone, where the impeller assembly 92 and the catheter body 84are coupled together. These high forces, if not carefully managed canresult in damage to the catheter assembly 80 and in some cases renderthe impeller within the impeller assembly 92 inoperable. A reliablemechanical interface is provided to assure high performance. While thisinterface is extremely beneficial for an assembly with an expandableimpeller disposed in an expandable cannula, it also applies toassemblies including a fixed diameter impeller, which may be disposed inan expandable cannula or even in a non-expandable portion in fluidcommunication with an expandable cannula. In one variation, the impelleris disposed proximal of an expandable cannula in a rigid segment (e.g.,a pump ring) and an expandable cannula is provided. The mechanicalinterfaces and inner and outer sheath assemblies facilitate the collapseof the cannula in such embodiments. A further design permits theimpeller to be withdrawn into a rigid structure, e.g., a pump ring, tocollapse the impeller before the cannula is collapsed.

The mechanical components rotatably supporting the impeller within theimpeller assembly 92 permit high rotational speeds while controllingheat and particle generation that can come with high speeds. Theimpeller may be rotated as speeds above 6000 RPM, above 9000 RPM, above10,000 RPM, above 15,000 RPM, above 20,000 RPM, above 25,000 RPM, orabove 30,000 RPM. The infusion system 26 delivers a cooling andlubricating solution to the distal portion of the catheter system 100for these purposes. However, the space for delivery of this fluid isextremely limited. Some of the space is also used for return of theinfusate. Providing secure connection and reliable routing of infusateinto and out of the catheter assembly 80 is critical and challenging inview of the small profile of the catheter body 84.

Various aspects of the pump and associated components are similar tothose disclosed in U.S. Pat. Nos. 7,393,181; 8,376,707; 7,841,976;7,022,100; and 7,998,054, and in U.S. Pub. Nos. 2011/0004046;2012/0178986; 2012/0172655; 2012/0178985; and 2012/0004495, the entirecontents of each of which are incorporated herein for all purposes byreference. In addition, this application incorporates by reference inits entirety and for all purposes the subject matter disclosed in eachof the following concurrently filed applications: application Ser. No.13/802,556, which corresponds to attorney docket no. THOR.072A, entitled“DISTAL BEARING SUPPORT,” filed on Mar. 13, 2013; Application No.61/780,656, which corresponds to attorney docket no. THOR.084PR2,entitled “FLUID HANDLING SYSTEM,” filed on Mar. 13, 2013; applicationSer. No. 13/802,570, which corresponds to attorney docket no. THOR.090A,entitled “IMPELLER FOR CATHETER PUMP,” filed on Mar. 13, 2013;application Ser. No. 13/801,528, THOR.093A, entitled “MOTOR ASSEMBLY FORCATHETER PUMP,” filed on Mar. 13, 2013.

FIGS. 4-6 show a first embodiment of a working end of a catheterassembly 100 forming a part of one embodiment of the catheter pump 10.The catheter assembly 100 is similar to the catheter system 84 except asdiscussed differently below. The catheter assembly 100 includes anelongate catheter body 104. A proximal end of the catheter body 104 canbe coupled with a motor housing. A distal portion of the catheter body104 is coupled to a cannula 108 configured to house a high flow rateimpeller 112. The exemplary catheter pump can be configured to producean average flow rate of 4 liters/minute or more at physiologicconditions, e.g., at the typical systolic pressure of a patient needingtreatment, such as 60 mmHg. In various embodiments, the pump can beconfigured to produce a maximum flow rate (e.g. low mm Hg) of greaterthan 4 Lpm, greater than 4.5 Lpm, greater than 5 Lpm, greater than 5.5Lpm, greater than 6 Lpm, greater than 6.5 Lpm, greater than 7 Lpm,greater than 7.5 Lpm, greater than 8 Lpm, greater than 9 Lpm, or greaterthan 10 Lpm. In various embodiments, the pump can be configured toproduce an average flow rate at 60 mmHg of greater than 2 Lpm, greaterthan 2.5 Lpm, greater than 3 Lpm, greater than 3.5 Lpm, greater than 4Lpm, greater than 4.25 Lpm, greater than 4.5 Lpm, greater than 5 Lpm,greater than 5.5 Lpm, or greater than 6 Lpm.

In some embodiments both the cannula 108 and the impeller 112 areactuatable from a first configuration for delivery through a patient toa working site to a second configuration for generating high flow at theworking site. The first configuration may be a low profile configurationand the second configuration may be an expanded configuration. The lowprofile configuration preferably enables access via a femoral artery orother peripheral blood vessel without excessive obstruction of bloodflow in the vessel, as discussed further below.

The catheter body 104 preferably has a plurality of lumens, including afirst lumen 140 adapted for housing a drive shaft 144, a second lumen140B for conveying a medical fluid distally within the catheter body104, and a third lumen 140C for anchoring a bearing housing 146 to thecatheter body 104. The drive shaft 144 extends proximally within thecatheter body 104 from the impeller 112. The drive shaft 144 coupleswith the motor at the proximal end and with the impeller 112 at thedistal end thereof. The drive shaft 144 can be formed with any suitablestructure, but should be sufficient flexible to traverse at least from aperipheral (e.g., femoral) artery to a heart chamber, such as the leftventricle, as well as sufficiently durable to rotate at a high speed forseveral hours, for several days, and in some cases, months. The driveshaft 144 can be coupled with an impeller assembly 112 including anexpandable impeller 112A) disposed on a tubular body 112B FIGS. 4 and 6shows these structures. The impeller 112A preferably includes anelastomeric polymer structure that can be formed as a unitary body. Thetubular body 112B can be a metal hypotube. The tubular body 112B can bereceived in a distal portion of the drive shaft 144.

Any suitable material or combination of materials can be used for thecatheter body 104 or catheter bodies 104A and 304 discussed below andprovided in some embodiments. In one embodiment, the catheter body 104has an inner layer 148 surrounding the lumen 140 that comprises highdensity polyethylene (HDPE). For example, Marlex 4903 HDPE can bedisposed about the lumen 140. If a composite structure is used to formthe catheter body 104, the inner layer 148 has a thickness that issufficient to withstand wear caused by interaction with the drive shaft144, which can be rotated at a very high speed in some applications, forexample from 20,000-40,000 revolutions per minute. The inner layer canhave a thickness of 0.003 inches.

The second lumen 140B extends from a proximal end in fluid communicationwith a source of infusate, which can be a medical fluid (e.g., saline),to a distal end adjacent to the impeller assembly 112. For example, thesecond lumen 140B can have an outlet disposed adjacent to a flow channelformed in or about the bearing housing 146. Examples of bearing housingflow channels are shown in FIGS. 5, 10 , and in application Ser. No.13/343,618, which is hereby incorporated by reference. In one embodimentof the catheter body 104A, the second lumen 140B is generallycircumferentially elongated, for example having two sides that arecurved with an arc length of about 0.030 inches and two sides that arestraight, disposed along a radial direction of the catheter body 104 andabout 0.010 inches in length. A proximal end of the second lumen 140B iscoupled with a port, which may be similar to the luer 145 in FIG. 2 , orother fluid connection device. Any suitable connection between a portand lumen can be used, e.g., a skived connection can be used.

The third lumen 140C can be used to enhance the security of theconnection between the catheter body 104, 104A and the bearing housing146. For example, the third lumen 140C can be sized to receive aplurality of, e.g., two, pull wires 160. The pull wires 160 can take anysuitable form, but preferably are sized to be easily received within thelumen 140C. In one embodiment, the lumen 140C is spaced apart from butabout the same size as the second lumen 140B and the pull wires aregenerally rectangular in shape, e.g., having a thickness of about 0.005inches and a width of about 0.010 inches. The pull wires 160 can beformed of any material that is sufficiently rigid in tension, e.g., ofstainless steel with pull strength of at least about 300 ksi. In onearrangement, the pull wires 160 extend at least about three inches intothe elongate body 104 in the third lumen 140C and extend out of thethird lumen 140C to overlay the bearing housing 146 as shown in FIG. 5 .

FIG. 6 shows one approach to compactly arranging the pull wires 160 andstructure coupled together thereby. In particular, a proximal portion160A of the wires is received within a distal length of the third lumen140C and a distal portion 160C of the wires is disposed distal of thecatheter body 104. A transition 160B is provided between the zones 160A,160C causing the proximal portion 160A to be disposed closer to thelongitudinal axis of the impeller catheter assembly 100 than is thedistal portion 160C. This permits the outer surface of the catheter body104 to be closer to the longitudinal axis of the catheter assembly 100than if the pull wires were straight with the distal portion 160C in thesame position as illustrated.

Providing a plurality of pull wires provides redundancy in theconnection between the catheter body 104, 104A and the bearing housing146. In some cases, this redundancy is not needed and a single wire canbe used. The redundancy is beneficial, however, because substantialtension force is applied at this connection point when the expandablecannula 108 is collapsed. In one technique relative motion is providedbetween the catheter body 104, 104A and an outer sheath disposed overthe catheter body until the outer sheath slides over a proximal portionof the cannula 108. Further relative motion causes the cannula 108 to becompressed, but not without a substantial force being applied thereto.This force is born at several points, including at the junction betweenthe catheter body 104, 104A and the bearing housing 146. Disconnectionof the bearing housing 146 would be problematic, requiring complexprocedures to extract the disconnected distal working end of thecatheter assembly 100.

The pull wires 160 preferably are located close together on the sameside of the catheter body 104, 104A. This arrangement enhances bendingflexibility, which is beneficial if tortuous vasculature must betraversed to deliver the catheter assembly 100 to a treatment site,e.g., a heart chamber. FIGS. 12-14 illustrate other techniques forenhancing the security of the connection of the bearing housing 146 to acatheter body.

In some embodiments, placing a radiopaque marker on a distal portion ofthe catheter assembly 100 is advantageous to confirm the location of theworking end, e.g., of the cannula 108 and/or impeller 112 prior toand/or after deployment.

Gross mechanical properties of the catheter body 104 can be varied alongthe length thereof to provide appropriate flexibility andmaneuverability within the vasculature to facilitate delivery andoperation of the catheter pump into which the catheter assembly 100 isincorporated. For example, in one embodiment, the catheter body 104 isstiffest near the distal end where the catheter body 104 is joined tothe working end. In one embodiment, a distal section of the catheterbody 104 comprises a material, such as Pebax, having a hardness of about72D. A proximal section of the catheter body 104 comprises a material,such as Vestamid having a hardness greater than about 72D. Between theserelatively hard sections ends, a middle section of the catheter bodycomprises a material having a lower hardness, e.g., MX1205 Pedbax. Thelow hardness section provides a softer structure in the vicinity of theaortic arch, where the catheter will be consistently resting on thevessel wall. One or more intermediate hardness sections can be providedbetween the distal, proximal and middle sections. These arrangements arealso relevant to the other inner catheter bodies discussed herein,including bodies 104A, 304.

Alternately, or in addition to these features, the catheter body 104 canhave different diameters along its length to provide several importantperformance benefits. The diameter of a proximal portion of the catheterbody 104 can be relatively large to enhance pushability and trackabilityof the catheter assembly 100. The diameter of a distal portion of thecatheter body 104 can be relatively small to enhance flexibility of thedistal tip and also to match the profile of the bearing housing 146 suchthat the lumens 140B align with flow channels at least partly defined bythe bearing housing (e.g., the slots 220 discussed below). The enlargeddiameter and enhanced hardness at the proximal end both contribute tothe maneuverability of the catheter assembly 100. These arrangements arealso relevant to the other inner catheter bodies discussed herein,including bodies 104A, 304 and the catheter assemblies 100A, 300, and400 (discussed below).

In addition to the foregoing structures for varying the stiffness alongthe length of the catheter body 104, a separate stiffening component,such as a braid 188, can be disposed in the catheter body 104, 104A. Inone embodiment, a 0.001 inch by 0.003 inch flat wire of 304V stainlesssteel is embedded in the catheter body 104, 104A and the braid includesa 70 ppi configuration. The braid 188 can be positioned in any suitablelocation, e.g., between an inner layer 148 and an outer layer, as shownin FIG. 9 of the drawings.

As discussed above, the catheter assembly 100 preferably also includesan outer sheath or sheath assembly 88 provided over the elongate body104, 104A to aid in delivering, deploying and/or removing the impeller112. The outer sheath 88 can include an elongate body 96 comprising aninner surface surrounding a lumen disposed therein. The inner lumen cancomprise a low friction material or layer. For example, a thickness ofPTFE can be provided adjacent the inner lumen. In one embodiment, one ormore separate materials can be provided at an outer surface of theelongate body 96.

The elongate body 96 preferably is connected at the proximal end with aproximal hub and/or a suitable connector, such as a Tuohy Borstconnector. The proximal hub can include a luer fitting.

The outer sheath 88 also may have varied hardness or other grossmechanical properties along its length to provide appropriateflexibility and maneuverability within the vasculature to facilitatedelivery and operation of the catheter pump into which the outer sheathis incorporated, and also to facilitate collapse of the cannula 108after deployment thereof. FIG. 6A illustrates schematically bulkproperty variation in two embodiments of the sheath assembly 88. Inparticular, an elongate body extending between the proximal and distalends of the sheath assembly 88 has different hardness at differentlocations along the length. The different hardnesses enhance themaneuverability of the sheath assemblies 88A, 88B to minimize kinking ofthe elongate body as the catheter assembly 100 is tracking toward theheart and/or when the elongate body is used to collapse an expandablecannula or impeller, as discussed elsewhere herein.

The elongate body of the sheath assembly 88A has a proximal portion “A”with a highest hardness. The proximal portion A can comprise vestamid orother similar material. A portion “B” distal of the proximal portion Aand residing over a zone of the cannula in which the impeller I and thedistal bearing support S (if present) are housed can have a hardnessthat is lower than that of the portion A. Portion B can comprise 55Dpebax. A portion “C” disposed distal of the portion B can comprise amaterial with the lowest hardness of the elongate body of the sheathassembly 88A, e.g., can comprise MX1205. A portion “D” at the distal endof the elongate body of the sheath assembly 88A can have a relativelyhigh hardness, e.g., 72D pebax. The sheath assembly 88A upon distalmovement over the expanded cannula initially contacts the cannula withthe relatively hard material of portion D. The relatively soft portion Cmay contact the vasculature as the catheter assembly 100 is advanced,and its relatively soft structure is biocompatible. Portion B has ahardness that is high enough to protect the zones I and S of thecannula, impeller, and support. Portion A is the hardest of thematerials used in the sheath assembly 88A, to aid in maneuverability.

The elongate body of the sheath assembly 88B has a proximal portion anddistal bearing zone portion “A” with a highest hardness. The proximalportion A can comprise vestamid or other similar material. A portion “B”between the proximal portion A and the distal bearing zone portion A.The portion B resides adjacent to the transition from the catheter body104 to the cannula proximal portion 116 and can have a hardness that islower than that of the portion A. Portion B can comprise 55D pebax.Portions C and D in the sheath assembly 88B are the same as in thesheath assembly 88A. A portion E is disposed between the portions A andC, e.g., distal of the portion A disposed over the distal bearingsupport. Portion E can include a series of progressively softer lengths,e.g., a first length of 72D pebax, a second length of 63D pebax, and athird length of 55D pebax. Other materials and hardnesses can be usedthat provide good resistance to kinking in the delivery of the catheterassembly 100 and/or in the process of re-sheathing the expanded cannulaand impeller.

FIGS. 7-10 incorporate the discussion above and illustrate additionalfeatures and embodiments. FIGS. 7 and 9 illustrate aspects of amechanical interface between a bearing housing 146A and the catheterbody 104A. In particular, a coupler 200 is provided between the bearinghousing 146A and the catheter body 104A. The coupler 200 (also shown inFIG. 6 ) is similar to the coupler 628 disclosed in U.S. applicationSer. No. 13/343,618, which is hereby incorporated by reference herein.In this configuration a thrust bearing 204 is provided in the bearinghousing 146A. In some embodiments, a thrust bearing brace 208 isdisposed just proximal of the thrust bearing 204. The thrust bearingbrace 208 can take any suitable form, but preferably provides a shoulderor other radial protrusion from the outer surface to the impeller shaft112B that abuts a proximal face of the thrust bearing 204. The thrustbearing brace 208 minimizes or completely prevents movement of thethrust bearing 204 on the impeller shaft 112B. Such movement is possiblebecause the impeller on the impeller shaft 112B generates significantdistally oriented thrust. In some assemblies, the thrust bearing 204 isinterference fit onto the impeller shaft 112B. When sized and fitproperly, this connection maintains the relative position of thrustbearing 204 to the impeller shaft 112B under the thrust forces that areapplied. The thrust bearing brace 208 provides redundancy of thisconnection. In one embodiment, the thrust bearing brace 208 comprises ashort hypotube that is coupled with, e.g., laser welded to the impellershaft 112B. The weld completely prevents relative axial movement betweenthe impeller shaft 112B and the thrust bearing brace 208. The abutmentbetween the trust bearing 204 and the thrust bearing brace 208 preventrelative movement between the thrust bearing 204 and impeller shaft 112Bif the coupling between the impeller shaft 112B and the thrust bearing204 loosens.

FIG. 8 shows that an outer surface of the bearing housing 146A can becovered by a cylindrical sleeve 216. The sleeve has at least one slot220 formed therein. The slot 220 can be circumferentially aligned to orotherwise in fluid communication with the second lumen 140B such thatinfusate fluid flowing distally in the lumen enters the slot and can bedirected distally in a space formed between the bearing housing 146A,the sleeve 216 and an outer sleeve, that may be a proximal portion 222of the frame-like structure of the cannula 108. This structure is shownin FIGS. 4 and 5 . In FIG. 4 , the cannula 108 is displaced proximallyto reveal the sleeve 216, which would be covered by a proximalcylindrical portion 222 of the cannula 108 when the catheter assembly100 is assembled. A difference between the impeller assembly/catheterbody interface of the embodiment of FIGS. 4-6 and the embodiment ofFIGS. 7-11 is that the sleeve 216A includes recess 220A in fluidcommunication with the lumen 140B. The recesses 220A are fluid flowstructures. Other ports into the inside of the bearing housing 146A canbe accessed through apertures 224 that do not extend to the proximal endof the sleeve 216. The apertures are fluid communication structuresthrough which fluid can flow into the bearing housing. Flow from thelumen 104B to the apertures 224 can be provided through acircumferential space defined between the outer surface of the sleeve216 and an inner surface of the proximal portion 222 of the cannula 108.See FIG. 10 . In some cases, the apertures 224 are additionally oralternately adapted to receive components of secondary mechanicalinterface discussed below. In other embodiments, troughs are formed inan outer surface of the bearing housing are enclosed by the innersurface of the sleeve 216 to form enclosed flow channels for infusate.

Catheter pumps incorporating the catheter assembly and variation thereofcan be configured to deliver average flow rates of over 4 liters/minutefor a treatment period. For example, a treatment period can be up to 10days for acute needs, such as patient in cardiogenic shock. Catheterpumps incorporating the catheter assembly 100 or such modificationsthereof can be used for shorter periods as well, e.g., for supportduring high risk catheter or surgical procedures.

Also, catheter pumps incorporating the catheter assembly 100 ormodifications thereof can be used for left or right side heart support.Example modifications that could be used for right side support includeproviding delivery features and/or shaping a distal portion that is tobe placed through at least one heart valve from the venous side, such asis discussed in U.S. Pat. Nos. 6,544,216; 7,070,555; and US2012-0203056A1, all of which are hereby incorporated by reference hereinin their entirety for all purposes. For example, the catheter assembly100 or modifications thereof can be configured to be collapsed to bedeliverable through a 13 French introducer sheath and can be expanded toup to 24 French when deployed. In one embodiment, the outer profile ofthe catheter assembly 100 or modifications thereof is approximately 12French, but can be any size that is insertable into a femoral arterywithout requiring surgical cutdown. The catheter assembly 100 can be aslarge as 12.5 F to be inserted through a 13French introducer sheath. Onemethod involves deployment of the cannula 108, having an expandablenitinol structure, across the aortic valve. In this position, theimpeller 112 can be disposed on the aorta side of the valve and a distallength of the cannula 108 within the ventricle.

In other embodiments, the outer profile of the catheter assembly 100 ormodifications thereof is less than 12 French, e.g., about 10 French. The10 French configuration can be useful for patients with lower flowneeds, e.g., about 3 liters per minute or less at physiologicconditions. In another example, an 8 French configuration can be usefulfor patients with lower flow needs, e.g., about 2 liters per minute orless at physiologic conditions.

FIGS. 11-14 illustrate additional embodiments in which the structuralintegrity of a catheter assembly 300 is enhanced to provide security inconnection with sheathing an expandable portion. FIG. 11 shows that adistal portion of the catheter assembly 300 includes components similarto those hereinbefore described. In particular, the catheter assembly300 includes a catheter body 304, an expandable cannula 308 and anexpandable impeller 312. The catheter body can take any suitable form.In one embodiment, the catheter body 304 has variable hardness along itslength.

The cannula 308 includes a self-expanding structure enclosed in apolymeric film. The self-expanding structure can be a distal portion ofa member having a non-expanding tubular portion 316 proximal of theself-expanding structure. The tubular portion 316 plays a role inanchoring the cannula 308 to the catheter body 304.

FIG. 11 shows that a support member 328 can be positioned within thecannula 308 to prevent unacceptable variance in the gap between the tipof the impeller 312 and the inside surface of the cannula. More detailsof this structure are set forth in concurrently filed application Ser.No. 13/802,556, which corresponds to attorney docket no. THOR.072A,entitled “DISTAL BEARING SUPPORT,” filed on Mar. 13, 2013, which isincorporated hereby by reference herein for all purposes. Successfulcollapse of the cannula 308, the impeller 312, and the support 328focuses forces on a joint between the cannula 308 and the catheter body304.

FIGS. 11-14 illustrate features that enhance the security of theconnection catheter body 304 and the cannula 308. In FIG. 11 , noseparate structure is shown between the catheter body 034 and thenon-expanding tubular portion 316. These structures are joined in othermanners, such as indirectly by the force transfer capability of the pullwires discussed above and/or by an adhesive. In FIG. 12 , the distal endof the catheter body 304 is coupled with a ferrule 336. The ferrule 336is an example of a structure to mechanically join the catheter body 304to the cannula 308. In one embodiment, the ferrule 336 includes a distalzone 340 for mechanically joining the ferrule 336 to the catheter body304. The distal zone 340 is also configured to mechanically couple withthe cannula 308, for example by welding. A plurality of apertures 344 isprovided in one embodiment for mechanically joining the ferrule 336 tothe catheter body 304. The apertures 344 enable the material of thecatheter body 304 to extend into the distal zone 340. In one techniquethe ferrule 336 is disposed over the catheter body 304 which extendsinto the apertures 344.

The apertures 344 can be arranged in multiple zones. In one embodiment afirst zone is disposed distally of the second zone. The first zone canbe disposed adjacent to the distal end of the ferrule 336 and the secondzone is disposed proximal of the first zone. The first zone can includefour apertures 344A spaced evenly about the periphery of the body of theferrule. The second zone can include a plurality of (e.g., four)apertures 344B spaced evenly about the periphery of the body of theferrule 336. A specific advantageous embodiment provides four apertures344B in the second zone. The apertures 344B of the second zone can bespaced evenly about the body of the ferrule 336. Preferably theapertures 344 of the first and second zones are offset to provide agreat deal of redundancy in the security of the connection of thecatheter body 304 to the ferrule 336. For example, the apertures 344 inthe first and second zones can be offset by one-half the circumferentialdistance between adjacent apertures 344.

The ferrule 336 also includes a proximal zone 348 disposed proximally ofthe aperture 344. The proximal zone 348 preferably is configured toprovide an excellent fluid seal between the ferrule and thenon-expandable tubular portion 316 of the cannula 308. In oneembodiment, the proximal zone 348 includes a plurality of recesses 352in the outer surface of the proximal portion 348. The recesses 352 cantake any form consistent with good sealing, and in one embodiment therecesses are turns of a continuous helical groove in the outer surfaceof the ferrule 336. The helical groove is configured to receive asealant that can bridge from the base of the grooves to the innersurface of the proximal portion 316 of the cannula 308. In oneembodiment, the sealant includes an adhesive that can flow into thehelical groove and be adhered to the inner surface of the proximalportion 316 of the cannula 308.

Although the weld and adhesive that can be formed or disposed betweenthe ferrule 336 and the proximal portion 316 of the cannula 308 canprovide excellent security between these components of the catheterassembly 300, a supplemental securement device 360 can be provided insome embodiments. FIG. 11 illustrates one embodiment in which amechanical securement device 360 is provided. The mechanical securementdevice 360 includes a cantilevered member that can be deformed from thenon-expandable proximal portion 316 of the cannula 308 intocorresponding recesses disposed inward of the securement device.

In one embodiment, a recess 364 is provided within the catheter assembly300 to receive the securement device 360. The recesses 364 can be formedin an internal structure disposed within the proximal portion 316. In afirst variation, a sleeve 368 is provided immediately within thenon-expandable proximal portion 316 of the cannula 308. The sleeve 368is provided and fills the volume between a bearing housing 372 and theproximal portion 316. The bearing housing 372 facilitates rotation ofthe impeller shaft and the flow of infusate. The sleeve 368 has slotsand/or other fluid communication structures formed therein that directflow from channels in the catheter body 308 to flow channels in thebearing housing 372. In one embodiment, the sleeve 368 has a pluralityof small apertures that are disposed between flow slots. The aperturesand slots can be similar is shape and form to the apertures 224 andslots 220 discussed above.

In other embodiment, apertures can be formed in the bearing housing 372.For example, the bearing housing 372 can have a plurality of channelsaligned with flow passages in the catheter body 304. In such embodiment,apertures for receiving the securement device 360 can be provideddirectly in the bearing housing 372. In another variation, apertures areprovided that extend through the sleeve 368 and into the bearing housing372.

Modifications of catheter pumps incorporating the catheter assembly 300can be used for right side support. For example, the elongate body 304can be formed to have a deployed shape corresponding to the shape of thevasculature traversed between a peripheral vascular access point and theright ventricle.

Any suitable manufacturing method can be used to cause a portion of thecatheter body 304 to be disposed in the apertures 344. For example, inone the catheter body 304 and the cannula 308 are to be joined. Thecannula 308 has the tubular portion 316 which is to be disposed over thecatheter body 304. The ferrule 336 is a metallic body that is animportant part of one form of a mechanical interface. The ferrule 336has an inner surface and apertures 344 that act as a first interfacezone and an outer surface that acts as a second interface zone. Theferrule 336 is positioned such that the inner surface is disposed overthe outer surface of short length of the catheter body 304 adjacent tothe distal end thereof.

In one technique, the outer surface of the catheter body 304 ismechanically coupled to the ferrule 336 by a process that involvesheating. The distal portion of the catheter body 304 and the ferrule 336are heated sufficiently to cause at least a portion of the catheter bodyto transition to a state with low resistance to deformation. The lowresistance state can be a fluid state or just a state in which thematerial of the catheter body 304 if more malleable. In the state havinglow resistance to deformation, the catheter body 304 flows through orprotrudes into the apertures 344. Because the material is formedcontinuously from a location inside the inner surface of the ferrule tooutside the inner surface, a strong mechanical coupling is providedbetween these components.

The tubular portion 316 of the cannula 308 can be coupled with theferrule 336 by any suitable technique. In one embodiment, the tubularportion 316 and the ferrule 336 are indirectly coupled through sleeve368 discussed more below. In particular, the distal end of the ferrule336 can be welded to the proximal end of the sleeve 368 and a secondconnection can be provided between the portion 316 and the sleeve asdiscussed elsewhere herein. In another embodiment, the ferrule 336 canbe directly connected by a suitable technique, such as welding ifsuitable materials are provided. These structures are also illustratedin FIG. 16 below, which shows further details of the connection by theferrule 336.

The foregoing technique of heating the catheter body 304 to cause thematerial thereof to be coupled with the proximal portion 160A of thepull wire(s) 160. Another technique for joining the pull wires 160 tothe catheter body 304 is by an epoxy or other adhesive at the proximalend of the wires and/or catheter body 304. A distal section of the pullwires 160 within the catheter body 304 can be left un-adhered to thecatheter body, such that this section of the pull wires 160 can moverelative to the catheter body or “float” to enhance flexibility of thedistal portion of the catheter body in some embodiments. The proximalportion 160A provides a first interface zone of a mechanical interfacebetween the catheter body 104 and the bearing housing 146. The distalportion 160C provides a second interface zone that can be coupled withthe bearing housing 146 by a suitable technique, such as welding. Inanother embodiment, the sleeve 216, 216A is formed of a material towhich the pull wires can be welded or otherwise mechanically secured.

FIG. 11 illustrates an additional optional feature that can facilitatetreatment with a catheter pump including the catheter assembliesdisclosed herein or any of the pumps discussed in U.S. application Ser.Nos. 13/343,618 and 13/343,617, which are hereby incorporated herein byreference. A deployment system is provided by combining the catheterassembly 300 (or any other discussed or claimed herein) with a guidewire guide 240. The guide wire guide 240 can be configured as a smallelongate tubular member sized to be advanced in a lumen formed in thedrive shaft 144. The guide wire guide 240 includes a lumen that is sizedto receive a guidewire (not shown). The wall thickness of the guide wireguide 240 is thin enough to fit within the allotted tolerance fortracking the catheter assemblies discussed herein through thevasculature. The guide wire guide 240 wall thickness is also thin enoughto permit the guide wire guide 240 to be withdrawn from between theguide wire and the catheter assembly once the guidewire is in placewithout damaging either of these structures or disrupting the positionof guidewire excessively. In various embodiments, the guide wire guide240 includes a self healing member that remains within the catheterassembly when the tubular portion is removed. The self-healing memberhas an end wall that re-seals when the guidewire is removed. Thus, theguide wire guide 240 facilitates loading the catheter assemblies onto aguidewire for a percutaneous delivery within a patient.

FIGS. 15-17 show details of a catheter assembly 400 having a statorassembly 402 disposed in a distal portion thereof. The stator assembly402 enhances the performance of a catheter pump including the catheterassembly 400. The stator assembly 402 can include a stator blade body404 having one or a plurality of, e.g., three, blades 408 extendingoutwardly from a central boy 412. The stator blade body 404 is at adownstream location of the impeller 312. In a percutaneous leftventricle application, the stator blade body 404 is disposed proximal ofthe impeller 312. In a percutaneous right ventricle application, thestator blade body 404 is located distal of the impeller 312. In atransapical approach to aid the left ventricle, which might be providedthrough ports in the chest wall or via thoracotomy or mini-thoracotomy,the stator blade body 404 is disposed distal of the impeller 312.

The stator blades 408 are configured to act on the fluid flow generatedby the impeller 312 to provide a more optimal fluid flow regimedownstream of the stator assembly 402. This fluid flow regime cancorrespond to a more optimal fluid flow regime out of the outlet of thecatheter pump. The stator blades 408 preferably convert at least theradial component of flow generated by the impeller 312 to a flow that issubstantially entirely axial. In some cases, the stator blades 408 areconfigured to reduce other inefficiencies of the flow generated by theimpeller 312, e.g., minimize turbulent flow, flow eddies, etc. Removingthe radial components of the flow can be achieved with blades that areoriented in an opposite direction to the orientation of the blades ofthe impeller 312, for example, clockwise versus counterclockwiseoriented blade surface.

While the stator blades 408 act on the flow generated by the impeller312, the fluids also act on the stator assembly 402. For example, thestator blade body 404 experiences a torque generated by the interactionof the blades 408 with the blood as it flows past the stator assembly402. A robust mechanical interface 420 is provided between the centralbody 412 and a distal portion of the catheter assembly 400. A bearinghousing 424 is provided that is similar to the bearing housing 372,except as described differently below. The bearing housing 424 includesan elongate portion 428 that projects into a lumen of the central body412. The elongate portion 428 preferably has an outer periphery that issmaller than an outer periphery of a portion of the bearing housing 424immediately proximal of the elongate portion 428.

This structure provides an interface 432 disposed between the elongateportion and the portion just distal thereto. The interface 432 can be ashoulder having a radial extent that is approximately equal to that ofthe central body 412. In some embodiments, a flush surface is providedbetween the outer surface of the central body 412 and a distal outersurface of the sleeve 368 such that the radial extent of the shoulder ofthe interface 432 is less than that of the central body 412 by an amountapproximately equal to the thickness of the sleeve 368. The interface432 can also or alternately includes an engagement feature between theinner surface of the lumen of the central body 412 and the outer surfaceof the elongate portion 428. In one embodiment, the outer surface of theelongate portion 428 has a helical projection or groove and the centralbody 412 has corresponding and mating helical grooves or projections.These features can be or can be analogous to screw threads. Preferablythe helix portion is arranged such that the torque felt by the statorassembly 402 generates a tightening of the engagement between theelongate portion 428 and the central body 412. The projections orgrooves in the central body 412 can be formed by molding the centralbody 412 over the elongate projection 428.

A small gap is provided between the stator assembly 402 and the impeller312 such that no or minimal contact is provided between thesecomponents, but the flow between the blades of these structures smoothlytransitions between the blades thereof. Such an arrangement is useful inthat the impeller 312 rotates at more than 10,000 RPM while the statorassembly 412 is stationary.

While the robust mechanical interfaces between the catheter body 104 andthe cannula 108 is important to the catheter assembly 300 the interfaceis even more important in certain embodiments of the catheter body 400that are actuated to a collapsed state prior to being removed from thepatient. In such embodiments, the deployed working end preferably iscollapsed, including the cannula 308, the stator blade body 404, and theimpeller 312. This can be done by providing distal relative motion ofthe sheath assembly 88. The forces applied by the sheath assembly 88 tothe catheter body 400, stator blade body 404, and the impeller 312 andfocused at the mechanical joints are enhanced due to the presence of thestator blade body 404.

One will appreciate from the description herein that the catheterassembly may be modified based on the respective anatomy to suit thedesired vascular approach. For example, the catheter assembly in theinsertion state may be shaped for introduction through the subclavianartery to the heart. The catheter pump may be configured for insertionthrough a smaller opening and with a lower average flow rate for rightside support. In various embodiments, the catheter assembly is scaled upfor a higher flow rate for sicker patients and/or larger patients.

Although the inventions herein have been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent inventions. It is therefore to be understood that numerousmodifications can be made to the illustrative embodiments and that otherarrangements can be devised without departing from the spirit and scopeof the present inventions as defined by the appended claims. Thus, it isintended that the present application cover the modifications andvariations of these embodiments and their equivalents.

1. A catheter pump assembly, comprising: a proximal portion; a distalportion; a catheter body having a lumen extending along a longitudinalaxis between the proximal and distal portions; an impeller disposed atthe distal portion; and a stator disposed adjacent the impeller in theblood flow path to straighten flow.
 2. The catheter pump assembly ofclaim 1, wherein the impeller and the stator are disposed in a cannulathrough which blood flows.
 3. The catheter pump assembly of claim 2,wherein the stator comprises stator blades extending radially toward thecannula.
 4. The catheter pump assembly of claim 3, wherein the statorblades are coupled to the cannula at discrete locations spaced apartcircumferentially around the cannula.
 5. The catheter pump assembly ofclaim 2, wherein the stator is disposed distal of the impeller.
 6. Thecatheter pump assembly of claim 5, wherein the stator functions as aninlet to the cannula.
 7. The catheter pump assembly of claim 1 furthercomprising an elongate sheath body having a retracted position in whichthe elongate sheath body is proximal of the cannula, and a forwardposition in which the elongate sheath body is disposed over the cannula.8. The catheter pump assembly of claim 1, further comprising a bearingassembly disposed adjacent to the impeller, the stator being disposed ona projection of the bearing assembly.
 9. The catheter pump assembly ofclaim 1, wherein the stator is disposed proximal of the impeller.
 10. Amethod of operating a catheter pump, comprising: insert a guidewire intoa vascular system of a patient and to the patient's heart; insert adistal portion of the catheter pump into the vascular system using theguidewire, the catheter pump further including a proximal portion and acatheter body having a lumen extending along a longitudinal axis betweenthe proximal and distal portions; turn an impeller disposed at thedistal portion to generate a blood flow over a path from the patient'sheart; and a stator disposed adjacent the impeller in the path of theblood flow to straighten the blood flow.
 11. The method of claim 10,wherein the impeller and the stator are disposed in a cannula throughwhich blood flows.
 12. The method of claim 11, wherein the statorcomprises stator blades extending radially toward the cannula.
 13. Themethod of claim 12, wherein the stator blades are coupled to the cannulaat discrete locations spaced apart circumferentially around the cannula.14. The method of claim 11, wherein the stator is disposed distal of theimpeller.
 15. The method of claim 14, wherein the stator functions as aninlet to the cannula.
 16. The method of claim 10 further comprising anelongate sheath body having a retracted position in which the elongatesheath body is proximal of the cannula, and a forward position in whichthe elongate sheath body is disposed over the cannula.
 17. The method ofclaim 10, further comprising a bearing assembly disposed adjacent to theimpeller, the stator being disposed on a projection of the bearingassembly.
 18. The method of claim 10, wherein the stator is disposedproximal of the impeller.